hideSoftInputFromWindow出现空指针错误

Question

我在这一行得到一个空指针异常:

public void hideKeyboard(){ 
InputMethodManager inputManager = (InputMethodManager)            
            this.getSystemService(Context.INPUT_METHOD_SERVICE);    
inputManager.hideSoftInputFromWindow(this.getCurrentFocus().getWindowToken(),      
            InputMethodManager.HIDE_NOT_ALWAYS);
}

这是从以下方法调用的:

@Override
public void onBackPressed() {
    super.onBackPressed();
    hideKeyboard();
}

这是唯一的活动.从片段中按下后退按钮.

堆:

09-28 19:14:40.301: E/InputEventSender(30324): Exception dispatching finished signal.
09-28 19:14:40.301: E/MessageQueue-JNI(30324): Exception in MessageQueue callback: handleReceiveCallback
09-28 19:14:40.325: E/MessageQueue-JNI(30324): java.lang.NullPointerException
09-28 19:14:40.325: E/MessageQueue-JNI(30324):  at com.example.ecohelp.MainActivity.hideKeyboard(MainActivity.java:75)
09-28 19:14:40.325: E/MessageQueue-JNI(30324):  at com.example.ecohelp.MainActivity.onBackPressed(MainActivity.java:31)
09-28 19:14:40.325: E/MessageQueue-JNI(30324):  at android.app.Activity.onKeyUp(Activity.java:2159)
09-28 19:14:40.325: E/MessageQueue-JNI(30324):  at android.view.KeyEvent.dispatch(KeyEvent.java:2647)
09-28 19:14:40.325: E/MessageQueue-JNI(30324):  at android.app.Activity.dispatchKeyEvent(Activity.java:2389)
09-28 19:14:40.325: E/MessageQueue-JNI(30324):  at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchKeyEvent(PhoneWindow.java:1860)
09-28 19:14:40.325: E/MessageQueue-JNI(30324):  at android.view.ViewRootImpl$ViewPostImeInputStage.processKeyEvent(ViewRootImpl.java:3791)
09-28 19:14:40.325: E/MessageQueue-JNI(30324):  at android.view.ViewRootImpl$ViewPostImeInputStage.onProcess(ViewRootImpl.java:3774)
09-28 19:14:40.325: E/MessageQueue-JNI(30324):  at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3379)
09-28 19:14:40.325: E/MessageQueue-JNI(30324):  at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:3429)
09-28 19:14:40.325: E/MessageQueue-JNI(30324):  at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:3398)
09-28 19:14:40.325: E/MessageQueue-JNI(30324):  at android.view.ViewRootImpl$AsyncInputStage.forward(ViewRootImpl.java:3483)
09-28 19:14:40.325: E/MessageQueue-JNI(30324):  at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:3406)
09-28 19:14:40.325: E/MessageQueue-JNI(30324):  at android.view.ViewRootImpl$AsyncInputStage.apply(ViewRootImpl.java:3540)
09-28 19:14:40.325: E/MessageQueue-JNI(30324):  at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3379)
09-28 19:14:40.325: E/MessageQueue-JNI(30324):  at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:3429)
09-28 19:14:40.325: E/MessageQueue-JNI(30324):  at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:3398)
09-28 19:14:40.325: E/MessageQueue-JNI(30324):  at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:3406)
09-28 19:14:40.325: E/MessageQueue-JNI(30324):  at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3379)
09-28 19:14:40.325: E/MessageQueue-JNI(30324):  at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:3429)
09-28 19:14:40.325: E/MessageQueue-JNI(30324):  at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:3398)
09-28 19:14:40.325: E/MessageQueue-JNI(30324):  at android.view.ViewRootImpl$AsyncInputStage.forward(ViewRootImpl.java:3516)
09-28 19:14:40.325: E/MessageQueue-JNI(30324):  at android.view.ViewRootImpl$ImeInputStage.onFinishedInputEvent(ViewRootImpl.java:3666)
09-28 19:14:40.325: E/MessageQueue-JNI(30324):  at android.view.inputmethod.InputMethodManager$PendingEvent.run(InputMethodManager.java:1982)
09-28 19:14:40.325: E/MessageQueue-JNI(30324):  at android.view.inputmethod.InputMethodManager.invokeFinishedInputEventCallback(InputMethodManager.java:1698)
09-28 19:14:40.325: E/MessageQueue-JNI(30324):  at android.view.inputmethod.InputMethodManager.finishedInputEvent(InputMethodManager.java:1689)
09-28 19:14:40.325: E/MessageQueue-JNI(30324):  at android.view.inputmethod.InputMethodManager$ImeInputEventSender.onInputEventFinished(InputMethodManager.java:1959)
09-28 19:14:40.325: E/MessageQueue-JNI(30324):  at android.view.InputEventSender.dispatchInputEventFinished(InputEventSender.java:141)
09-28 19:14:40.325: E/MessageQueue-JNI(30324):  at android.os.MessageQueue.nativePollOnce(Native Method)
09-28 19:14:40.325: E/MessageQueue-JNI(30324):  at android.os.MessageQueue.next(MessageQueue.java:132)
09-28 19:14:40.325: E/MessageQueue-JNI(30324):  at android.os.Looper.loop(Looper.java:124)
09-28 19:14:40.325: E/MessageQueue-JNI(30324):  at android.app.ActivityThread.main(ActivityThread.java:5103)
09-28 19:14:40.325: E/MessageQueue-JNI(30324):  at java.lang.reflect.Method.invokeNative(Native Method)
09-28 19:14:40.325: E/MessageQueue-JNI(30324):  at java.lang.reflect.Method.invoke(Method.java:525)
09-28 19:14:40.325: E/MessageQueue-JNI(30324):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
09-28 19:14:40.325: E/MessageQueue-JNI(30324):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
09-28 19:14:40.325: E/MessageQueue-JNI(30324):  at dalvik.system.NativeStart.main(Native Method)

Answer 1

我只需要在隐藏键盘之前检查是否有焦点视图.

例如,如果您EditText的活动或片段中有一个,那么它可能就是焦点视图.当EditText不再聚焦时,getCurrentFocus()可以返回null(除非聚焦其他视图).

void hideKeyboard() {
    InputMethodManager inputManager = (InputMethodManager) getActivity().getSystemService(
            Context.INPUT_METHOD_SERVICE);
    View focusedView = getActivity().getCurrentFocus();
    /*
     * If no view is focused, an NPE will be thrown
     * 
     * Maxim Dmitriev
     */
    if (focusedView != null) {
        inputManager.hideSoftInputFromWindow(focusedView.getWindowToken(),
                InputMethodManager.HIDE_NOT_ALWAYS);
    }
}

Answer 2

正如CommonsWare所提到的,getCurrentFocus()为null,因为当前Activity中没有View组件持有焦点.

如果您的Activity中已有视图,请使用它来获取窗口令牌.例如,如果我有一个Button组件:

inputManager.hideSoftInputFromWindow(myButton.getWindowToken(), InputMethodManager.HIDE_NOT_ALWAYS);

或者更糟糕的是,如果我的Activity中没有任何视图,我可以这样做:

inputManager.hideSoftInputFromWindow(new View(this).getWindowToken(), InputMethodManager.HIDE_NOT_ALWAYS);

这可以解决你的NPE问题,但我希望你发现这个描述很有用.

关于键盘的另一个问题是当用户在键盘可见时按下后退按钮时,键盘接收并消耗后退按键以隐藏自身.或者至少大多数键盘都是这样的.

Answer 3

以上所有人都正确指出getWindowToken()返回null.

getCurrentFocus().getWindowToken()当我遇到同样的问题时,我使用默认代码隐藏键盘.

然后我意识到,由于没有View获得焦点,我得到了NullPointerException.

我们可以将以上内容更改为:

anyView.getWindowToken()

anyView您的布局中的任何视图都在哪里.

Answer 4

我有同样的问题,其中getCurrentFocus()返回null.所以这个方法对我有用,我会在我的onClick上调用它来隐藏键盘,如果它显示或者仍然没有抛出空指针异常,即使键盘没有显示:

public void hiddenInputMethod() {

    InputMethodManager imm = (InputMethodManager) getSystemService(MyActivity.this.INPUT_METHOD_SERVICE);
    if (getCurrentFocus() != null)
        imm.hideSoftInputFromWindow(this.getCurrentFocus().getWindowToken(), InputMethodManager.HIDE_NOT_ALWAYS);
}

Answer 5

如果要在触摸屏幕时隐藏键盘，请使用以下代码

       @Override
public boolean onTouchEvent(MotionEvent event) {
    InputMethodManager imm = (InputMethodManager)this.getSystemService(Context.
            INPUT_METHOD_SERVICE);
    imm.hideSoftInputFromWindow(this.getWindow().getDecorView().getRootView().getWindowToken(), 0);
    return true;
}

如果要在特定视图中执行此操作（EditText）

      public void  hideKeyBoard(EditText edt) {
    InputMethodManager imm = (InputMethodManager)this.getSystemService(Context.
            INPUT_METHOD_SERVICE);
    imm.hideSoftInputFromWindow(edt.getWindowToken(), 0);

}

或者您可以使用任何视图。

获取当前视图

    imm.hideSoftInputFromWindow(this.getWindow().getDecorView().getRootView().getWindowToken(), 0);

Answer 6

这对我有用。只需添加以下getWindow（）。getDecorView（）。getRootView（）。getWindowToken（）即可，而不是使用getCurrectFocus（）。之后，您可以在活动中的任何位置使用此方法。

public static void hideSoftKeyboard(Activity activity) {
        InputMethodManager inputMethodManager =
                (InputMethodManager) activity.getSystemService(
                        Activity.INPUT_METHOD_SERVICE);
        inputMethodManager.hideSoftInputFromWindow(
                activity.getWindow().getDecorView().getRootView().getWindowToken(), 0);
    }

Answer 7

尝试这个：

public void hideKeyboard(){ 
InputMethodManager inputManager = (InputMethodManager)            
            this.getSystemService(Context.INPUT_METHOD_SERVICE);    
inputManager.hideSoftInputFromWindow(this.getCurrentFocus().getWindowToken(), 0);
}